This proposal is in response to the recommendations issued by the National Institute of Aging (NIA) sponsored Research Planning Workshop on Sleep and Aging. The penile erectile process is a fundamental aspect of human sexual function. The mechanisms involved in erectile function depend upon complex interaction and coordination of psychological, neuroendocrine and various central nervous system (CNS) activities. Over the last decade and a half, we have investigated various aspects of the relationship between sleep and human penile erectile function. Aside from perfecting a device to measure nocturnal penile tumescence (NPT), we have established age-group norms (ages 3-79) for the changes in penile circumference which occur during sleep. The results of our experiments have demonstrated that sleep polysomnography is a useful tool for quantitatively investigating erectile mechanism and diagnosing erectile dysfunction. The major objective of the present research project is to apply our methodologies to aging populations such that age-related changes in NPT and potency may be determined. To accomplish this objective we will examine the following relevant variables: (1) Sleeping NPT, (2) sleep electrodermal activity, (3) neuroendocrine levels, (4) neurometric parameters, and (5) psychological-neuropsychological test performance. This project's multidisciplinary approach to the problems of erectile dysfunction in aging offers a unique opportunity in that it will be feasible to advance the understanding of NPT and evaluate pathophysiologies involved in impotence among the elderly.